In a protein on the surface of osteoclasts, to

In RA the immune system attacks joints and organ tissues. The white blood cell of the immune system move into the joint. They release chemicals which attack the cells of the synovial membrane. The chemicals cause cells to release other destructive substances. They also cause the synovial membrane to grow new blood vessels and form a thickened area called a pannus. Over time, the pannus can damage cartilage and other soft tissues and also erode bone. Inflammation causes fluid buildup in the joint making the joint swell. Eventually without treatment, the joint space narrows and ankylosis can occur. Ankylosis is fusion or growing together of bones in the joint. This result in the loss of the ability to move the joint (Tyty, 2017).  Activated synovial cells also secrete proteases which break down and the proteins in the articular cartilage. Without the protective cartilage, the underlying bones are exposed and can directly rub against one another. In addition, inflammatory cytokines increase a protein on the surface of T-cells, known as RANKL or receptor activator of nuclear factor kappa-B ligand. RANKL allows the T-cells to bind RANK, a protein on the surface of osteoclasts, to get them to start breaking down bones (Lubberts, et al., 1970). Meanwhile, antibodies also enter the joint space. One antibody is called rheumatoid factor, or RF, which is an IGM antibody that targets the constant Fc domain of altered IgG antibodies. Another antibody is an anti-cyclic citrullinated peptide antibody, which targets citrullinated proteins. An immune complexes is formed when these antibodies bind to their target which then accumulate in the synovial fluid. In there, the antibodies begin to activate the complement system, a family of nine small proteins that work in an enzymatic stream to cause joint inflammation and injury. At the end, the chronic inflammation causes angiogenesis, or the formation of new blood vessels around the joint, this allows more inflammatory cells to arrive. As the disease progresses, multiple joints on both sides of the body get inflamed and gradually destroyed